Conventional breathing assistance systems typically include a gas delivery system (e.g., a ventilator, CPAP device, etc.), a patient interface (e.g., nasal mask, face mask, nasal pillows, endotrachael tube, etc.) to deliver gas to one or more breathing passages of the patient, and a connection system (e.g., patient circuit) between the gas delivery system and the patient interface. Such breathing assistance systems may be used, e.g., for mechanical ventilation of a patient's lungs and/or treatment of an apnea or other medical condition.
Some breathing assistance systems include one or more sensors for measuring parameters related to the patient (e.g., the patient's breath rate, heart rate, etc.), the gas flow delivered to the patient (e.g., the flow rate, pressure, etc.), and/or various other parameters. In some systems, sensor(s) for measuring parameters at the patient end of the system are located at or near the patient interface (e.g., nasal mask) and physically connected to a control unit of the gas delivery system by wires running through or integrated with the patient circuit. In other systems, sensor(s) for measuring parameters at the patient end of the system are located at or near the gas delivery system, and algorithms are applied to the sensor measurements in order to approximate the measurements of such parameters at the patient end of the system (e.g., to correct for the pressure drop that occurs between the gas delivery system and the patient).